Overhead transfer flange and support for suspending a substrate carrier

ABSTRACT

In a first aspect, a first apparatus is provided for use in supporting a substrate carrier. The first apparatus includes an overhead transfer flange adapted to couple to a substrate carrier body and an overhead carrier support. The overhead transfer flange has a first side and a second side opposite the first side that is wider than the first side. Numerous other aspects are provided.

This application is a continuation of and claims priority to U.S. patent application Ser. No. 10/764,820, filed Jan. 26, 2004, which claims priority to U.S. Provisional Application Ser. No. 60/443,153, filed Jan. 27, 2003. Each of these applications is hereby incorporated by reference herein in its entirety for all purposes.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is related to the following commonly-assigned, co-pending U.S. patent applications, each of which is hereby incorporated by reference herein in its entirety:

U.S. patent application Ser. No. 10/650,310, filed Aug. 28, 2003 and titled “System For Transporting Substrate Carriers”;

U.S. patent application Ser. No. 10/650,312, filed Aug. 28, 2003 and titled “Method and Apparatus for Using Substrate Carrier Movement to Actuate Substrate Carrier Door Opening/Closing”;

U.S. patent application Ser. No. 10/650,481, filed Aug. 28, 2003 and titled “Method and Apparatus for Unloading Substrate Carriers from Substrate Carrier Transport Systems”;

U.S. patent application Ser. No. 10/650,479, filed Aug. 28, 2003 and titled “Method and Apparatus for Supplying Substrates to a Processing Tool”;

U.S. Patent Application Ser. No. 60/407,452, filed Aug. 31, 2002 and titled “End Effector Having Mechanism For Reorienting A Wafer Carrier Between Vertical And Horizontal Orientations”;

U.S. Patent Application Ser. No. 60/407,337, filed Aug. 31, 2002, and titled “Wafer Loading Station with Docking Grippers at Docking Stations”;

U.S. patent application Ser. No. 10/650,311, filed Aug. 28, 2003 and titled “Substrate Carrier Door having Door Latching and Substrate Clamping Mechanism”;

U.S. patent application Ser. No. 10/650,480, filed Aug. 28, 2003 and titled “Substrate Carrier Handler That Unloads Substrate Carriers Directly From a Moving Conveyor”;

U.S. Provisional Application Ser. No. 60/443,087, filed Jan. 27, 2003 and titled “Methods and Apparatus for Transporting Wafer Carriers”;

U.S. Provisional Application Ser. No. 60/443,001, filed Jan. 27, 2003, and titled “Systems and Methods for Transporting Wafer Carriers Between Processing Tools”; and

U.S. Provisional Application Ser. No. 60/443,115, filed Jan. 27, 2003, and titled “Apparatus and Method for Storing and Loading Wafer Carriers”.

FIELD OF THE INVENTION

The present invention relates generally to semiconductor device manufacturing, and more particularly to an overhead transfer flange of a substrate carrier and a support for suspending the substrate carrier via the overhead transfer flange.

BACKGROUND OF THE INVENTION

Semiconductor devices are made on substrates, such as silicon substrates, glass plates, etc., for use in computers, monitors, and the like. These devices are made by a sequence of fabrication steps, such as thin film deposition, oxidation or nitridization, etching, polishing, and thermal and lithographic processing. Although multiple fabrication steps may be performed in a single processing station, substrates typically must be transported between processing stations for at least some of the fabrication steps.

Substrates generally are stored in cassettes or pods (hereinafter referred to collectively as “substrate carriers”) for transfer between processing stations and other locations. Although substrate carriers may be carried manually between processing stations, the transfer of substrate carriers is typically automated. For instance, automatic handling of a substrate carrier may be performed by a robot, which lifts the substrate carrier by means of an end effector. As one example, end effectors have been proposed that lift a substrate carrier by engaging a flange provided at the top of the substrate carrier. One known type of end effector includes a support plate and fingers extending downwardly and inwardly from the support plate to define a “T”-shaped slot. The slot may be moved horizontally over and around the carrier flange. Pins may be provided that protrude upwardly from the end effector fingers to mate with detents provided on the flange.

Successful transport and transfer of substrate carriers requires that a substrate carrier position be controlled with a high degree of precision. It is desirable to provide a substrate carrier support and an overhead transfer flange that together facilitate proper substrate carrier positioning.

SUMMARY OF THE INVENTION

In a first aspect of the invention, a first apparatus is provided for use in supporting a substrate carrier. The first apparatus includes an overhead transfer flange adapted to couple to a substrate carrier body and an overhead carrier support. The overhead transfer flange has a first side and a second side opposite the first side that is wider than the first side.

In a second aspect of the invention, a substrate carrier is provided. The substrate carrier includes (1) a substrate carrier body adapted to support one or more substrates; and (2) an overhead transfer flange coupled to the substrate carrier body and adapted to couple to an overhead carrier support. The overhead transfer flange has a first side and a second side opposite the first side that is wider than the first side.

In a third aspect of the invention, a second apparatus is provided for use in supporting a substrate carrier. The second apparatus includes an overhead carrier support adapted to suspend a substrate carrier via an overhead transfer flange. The overhead carrier support has a first side and a second side opposite the first side that is wider than the first side. Numerous other aspects, as are methods and systems in accordance with these and other aspects of the invention.

Other features and aspects of the present invention will become more fully apparent from the following detailed description of exemplary embodiments, the appended claims and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective elevational view of a portion of an overhead transfer conveyor, as the overhead transfer conveyor transports a first and a second carrier;

FIG. 2 is a perspective elevational view, exploded along the in-line direction, of the assembly of the overhead carrier support and the overhead transfer flange shown in FIG. 1;

FIG. 3 is a bottom plan view, of the exploded assembly of the overhead carrier support and the overhead transfer flange shown in FIG. 2;

FIG. 4 is a bottom plan view of the exploded assembly of the overhead carrier support and the overhead transfer flange shown in FIG. 2;

FIGS. 5 and 6 are perspective views of respective portions of the first blade receiver of the overhead carrier support, and of the first blade of the overhead transfer flange (including cross-sections);

FIGS. 7-8 are simple cross-sectional views of the same portions of the overhead carrier support and the overhead transfer flange;

FIG. 9 is a perspective cut-away view of a portion of the overhead transfer conveyor of FIG. 1 utilizing the inventive coupling between the overhead carrier support and the overhead transfer flange, wherein an object, present in the path through which the overhead transfer conveyor carries a carrier, strikes the carrier;

FIGS. 10-12 are cross-sectional views of respective portions of the first blade receiver of the overhead carrier support, and the first blade of the overhead transfer flange, which depict a decoupling process that results in a carrier dislodging from the overhead transfer conveyor of FIG. 1;

FIG. 13 is a cross sectional view of a portion of the first blade receiver of the overhead carrier support and of the first blade of the overhead transfer flange illustrating an alternative embodiment of such components;

FIG. 14 is a perspective view of a plurality of shelves configured to support substrate carriers via an overhead transfer flange in accordance with the present invention; and

FIG. 15 is a perspective view of the shelves of FIG. 14 wherein the top shelf supports a substrate carrier via its overhead transfer flange.

DETAILED DESCRIPTION

The present invention provides an overhead transfer flange for a substrate carrier and a corresponding overhead support for supporting the carrier via the overhead transfer flange. The substrate carrier may be a single substrate carrier adapted to store only one substrate or a multiple substrate carrier adapted to store a plurality of substrates. In one aspect, the overhead support is adapted such that the support provides a capture window (for capturing the overhead transfer flange) that varies from a wider window to a narrower window in a direction in which the overhead transfer flange can approach the support. In a second aspect the overhead transfer flange and overhead support are adapted such that when the overhead transfer flange is supported by the overhead support, the overhead transfer flange is prevented from moving relative to the overhead support in any direction except vertically. In a further aspect the overhead transfer flange and overhead support are adapted such that if a substrate carrier supported thereby is impacted in a direction opposite to the direction in which the carrier is traveling, the carrier's overhead transfer flange will decouple from the overhead support, allowing the carrier to fall.

Each of these aspects is considered inventive on its own, however, in at least one embodiment the overhead transfer flange and overhead support may embody each of the aspects described above. The figures and the following description thereof provide a specific configuration that embodies each of the inventive aspects identified above. The configuration of FIGS. 1-12, is merely exemplary and it will be understood that alternative configurations may be designed that function in accordance with the invention.

FIG. 1 is a perspective elevational view of a portion 101 of an overhead transfer conveyor 103, as the overhead transfer conveyor 103 transports a first and a second carrier 105 a, 105 b in a first in-line direction 107 along a moveable track 109 of the overhead transfer conveyor 103. An inventive first overhead carrier support 111 a of the overhead transfer conveyor 103 supports the first carrier 105 a via an inventive first overhead transfer flange 113 a fixed to and centered above the first carrier 105 a, and an inventive second overhead carrier support 111 b of the overhead transfer conveyor 103 supports the second carrier 105 b via an inventive second overhead transfer flange 113 b fixed to and centered above the second carrier 105 b. Other positions of the overhead transfer flanges 113 a, 113 b relative to the substrate carriers 105 a, 105 b may be employed.

FIG. 2 is a perspective elevational view, exploded along the in-line direction 107, of the assembly of the overhead carrier support 111 a and the overhead transfer flange 113 a shown in FIG. 1. The overhead carrier support 111 a comprises a support plate 115 and a coupling clamp 117 fixed atop the support plate 115 and adapted to securely couple the overhead carrier support 111 a to the moveable track 109 of the overhead transfer conveyor 103. The overhead carrier support 111 a further includes a flexible hanger 119, also fixed atop the support plate 115, and adapted to provide additional support for the overhead carrier support 111 a along the moveable track 109. A first blade receiver 121 a is fixed below a first side 123 a of the support plate 115, and a second blade receiver 121 b is fixed below a second side 123 b of the support plate 115, opposite the first side 123 a. The various components of the overhead carrier support 111 a may be coupled together using any suitable coupling mechanism (e.g., screws, bolts, adhesives, etc.). All or a portion of the components of the overhead carrier support 111 a may be integrally formed.

The overhead transfer flange 113 a comprises a flange plate 125 adapted to attach to a carrier (e.g., the first carrier 105 a (FIG. 1)) via a suitable fastening mechanism such as fastener holes 127 or the like. A first blade 129 a extends down from a first side 131 a of the flange plate 125, and a second blade 129 b (obscured in FIG. 2 but see FIG. 3) extends down from a second side 131 b of the flange plate 125. A stiffening extension 133 extends down from a third side 131 c of the flange plate 125.

As will be explained further below, the first blade receiver 121 a is adapted to receive the first blade 129 a, and the second blade receiver 121 b is adapted to receive the second blade 129 b. And as will be also explained further below, the support plate 115, the first blade receiver 121 a, and the second blade receiver 121 b of the overhead carrier support 111 a define an overhead flange capture window 137 through which the overhead transfer flange 113 a is adapted to pass prior to the first and second blade receivers 121 a, 121 b of the overhead carrier support 111 a receiving the respective first and second blades 129 a, 129 b of the overhead transfer flange 113 a.

FIG. 3 is a bottom plan view of the exploded assembly of the overhead carrier support 111 a and the overhead transfer flange 113 a shown in FIG. 2. The overhead carrier support 111 a and the overhead transfer flange 113 a are aligned along a vertical plane 135 coinciding with a centerplane 135A of the overhead carrier support 111 a and a centerplane 135B of the overhead transfer flange 113 a. Referring to FIG. 1, the vertical plane 135 is preferably aligned with the vertically-oriented moveable track 109 of the overhead transfer conveyor 103, however other orientations (e.g., at an angle, or parallel but offset) can also be provided in accordance with the present invention.

The overhead flange capture window 137 appears as a line in the view of FIG. 3. The overhead carrier support 111 a is adapted to permit the overhead transfer flange 113 a to advance toward the overhead carrier support 111 a from the relative position of the overhead transfer flange 113 a shown in the view of FIG. 3 and through the overhead flange capture window 137.

The first blade receiver 121 a is oriented at a first angle 139 a to the centerplane 135A of the overhead carrier support 111 a, and the second blade receiver 121 b is oriented at a second angle 139 b to the centerplane 135A of the overhead carrier support 111 a. Preferably, the first angle 139 a and the second angle 139 b are equivalent so that the second blade receiver 121 b mirrors the first blade receiver 121 a from across the centerplane 135A of the overhead carrier support 111 a. In one embodiment, a third angle 141 between the first blade receiver 121 a and the second blade receiver 121 b is about 60 degrees. Other angles may be employed (e.g., including angles as small as about 10-20 degrees). As will be apparent, the selection of the extent of the third angle 141 is related to other aspects of the geometry of the overhead carrier support 111 a and the overhead transfer flange 113 a, as will be explained below.

The first blade 129 a is oriented at a fourth angle 139 c to the centerplane 135B of the overhead transfer flange 113 a, and the second blade 129 b is oriented at a fifth angle 139 d to the centerplane 135B of the overhead transfer flange 113 a. Preferably, the fourth angle 139 c and the fifth angle 139 d are equivalent so that the second blade 129 b mirrors the first blade 129 a from across the centerplane 135B of the overhead transfer flange 113 a. In one embodiment, a sixth angle 143 between the first blade 129 a and the second blade 129 b is about 60 degrees. Other angles may be employed. For proper interaction between the overhead carrier support 111 a and the overhead transfer flange 113 a, the third angle 141 and the sixth angle 143 are preferably substantially equivalent.

FIG. 4 is a bottom plan view of the exploded assembly of the overhead carrier support 111 a and the overhead transfer flange 113 a shown in FIG. 2. FIG. 4 is similar to FIG. 3 except that the overhead transfer flange 113 a has advanced from the position relative to the overhead carrier support 111 a (see phantom outline) that is occupied in the view of FIG. 3, passed through the overhead flange capture window 137, and is shown in a nested position with respect to the overhead carrier support 111 a. In this nested position, the first and second blades 129 a, 129 b, which together substantially form a cropped “V” shape or a cropped chevron, are in close spaced relation with the respective first and second blade receivers 121 a, 121 b (which also substantially form a cropped “V” shape or a cropped chevron), but are not yet mated with the same. This may be referred to as a staging position for the overhead transfer flange 113 a.

Although advancement of the overhead transfer flange 113 a through the overhead flange capture window 137 may be employed to mate the overhead transfer flange 113 a with the overhead carrier support 111 a, the present invention provides, and the discussion below explains, that the overhead transfer flange 113 a also can be raised up from below the overhead carrier support 111 a to assume the nesting position of FIG. 4 (rather than approaching with a horizontal component). A continuation of the in-line advancement similar to that shown in FIG. 4 can then take place for the first blade 129 a and the second blade 129 b of the overhead transfer flange 113 a to respectively mate with and be securely supported by the first blade receiver 121 a and the second blade receiver 121 b of the overhead carrier support 111 a. Section V-V as depicted in FIG. 4 is representative of the cross-sections cut normal to the first blade receiver 121 a and the first blade 129 a as shown and described below with reference to FIGS. 5-12.

FIGS. 5 and 6 are perspective views of respective portions of the first blade receiver 121 a of the overhead carrier support 111 a, and of the first blade 129 a of the overhead transfer flange 113 a (including cross-sections), and FIGS. 7-8 are simple cross-sectional views of the same portions of the overhead carrier support 111 a and the overhead transfer flange 113 a. FIGS. 5-8 depict the coupling process that results in the first blade receiver 121 a and the second blade receiver 121 b (not shown) of the overhead carrier support 111 a supporting the first blade 129 a and the second blade 129 b (not shown) of the overhead transfer flange 113 a.

During the coupling process depicted in FIGS. 5-8, the first blade receiver 121 a (shown coupled to, and below, the support plate 115 of the overhead transfer flange 113 a) and the first blade 129 a move relative to each other, and the second blade receiver 121 b (not shown) and the second blade 129 b (not shown) also move relative to each other. As between each respective pairing of blade and blade receiver, the relative motion is substantially similar, except that a relative motion between the second blade receiver 121 b (not shown) and the second blade 129 b (not shown) will tend to be the reverse of, or the mirror-image of, the relative motion between the first blade receiver 121 a and the first blade 129 a shown in FIGS. 5-8 and FIGS. 10-12. As such, FIGS. 5-8 and FIGS. 10-12 illustrate only the relative motion between the first blade receiver 121 a and the first blade 129 a, with the relative motion of the other blade-blade receiver pairing being understood to be the mirror image of the same.

In FIGS. 5-8, as well as in FIGS. 10-12, the support plate 115 and first blade receiver 121 a are shown as two pieces, coupled together. However, the support plate 115 and the first blade receiver 121 a may be a single piece.

Referring to FIG. 5, a first receiving surface 121 aa of the first blade receiver 121 a is preferably planar, and is adapted to slidably communicate with a first blade surface 129 aa (obscured) of the first blade 129 a, also preferably planar, in conjunction with the first blade receiver 121 a mating with the first blade 129 a. A second receiving surface 121 ab (obscured) of the first blade receiver 121 a is also preferably planar, and is adapted to contact a first blade edge 129 ab of the first blade 129 a. In at least one embodiment of the invention, the first blade edge 129 ab is adapted to settle into the first blade receiver 121 a by the force of gravity and achieve contact with an extended vertex 121 ac of the first blade receiver 121 a, defined by the intersection between the first blade receiver's first receiving surface 121 aa and the first blade receiver's second receiving surface 121 ab. The first receiving surface 121 aa of the first blade receiver 121 a is also adapted to achieve contact with the first blade edge 129 ab if necessary. An elongated lip 121 ad of the first blade receiver 121 a is preferably located at a right most extent 121 ae of the first blade receiver 121 a. Other locations of the lip 121 ad may be employed.

The first blade 129 a of the overhead transfer flange 113 a is shown in FIG. 5 in a convenient staging position relative to the first blade receiver 121 a of the overhead carrier support 111 a as shown and described above with reference to FIG. 4, the view being that of section V-V, as indicated in FIG. 4. One reason why this staging position is convenient is because the first blade 129 a is close to a lodging position within the first blade receiver 121 a, requiring only to be urged toward the first blade receiver 121 a in the in-line direction 107 (see FIG. 1) and lowered with respect to the first blade receiver 121 a to achieve such lodging. Another reason why the staging position shown is convenient is that the first blade 129 a can reach the position from multiple staging position access directions (e.g., a first staging position access direction 145 a, a second staging position access direction 145 b, etc.).

The first staging position access direction 145 a is the horizontal access direction as shown and described with reference to FIG. 4 above. If sufficient in-line spacing exists between successive carrier supports (e.g., between the first carrier 105 a and the second carrier 105 b of FIG. 1) along the conveyor (e.g., the overhead transfer conveyor 103 of FIG. 1), the first staging position access direction 145 a can easily be accommodated, and has the advantage of continuity and simplicity, since a simple continuation of motion of the overhead transfer flange 113 a in the in-line direction 107 (see FIG. 1), past the staging position shown, is required to place the first blade 129 a directly above a lodging position within the first blade receiver 121 a.

The second staging position access direction 145 b is a practical alternative to the first staging position access direction 145 a when carriers are closely spaced along the conveyor (e.g., as closely spaced as the first carrier 105 a and the second carrier 105 b are along the moveable track 109 of the overhead transfer conveyor 103 as shown in FIG. 1). The second staging position access direction 145 b is a vertical access direction, and it takes advantage of the fact that the chevron formed by the first blade 129 a and the second blade 129 b can nest closely behind the chevron formed by the first blade receiver 121 a and the second blade receiver 121 b without the blades coming in contact with the blade receivers 121 a, 121 b.

Because the chevron formed by the first blade 129 a and the second blade 129 b can nest behind the chevron formed by the first blade receiver 121 a and the second blade receiver 121 b, the overhead transfer flange 113 a can rise up from below the overhead carrier support 111 a and move upwards past the first blade receiver lip 121 ad and past the rightmost extent 121 ae of the first blade receiver 121 a, such that the first blade 129 a rises above the first blade receiver 121 a from behind the first blade receiver 121 a (e.g., behind in the in-line direction 107) to reach the convenient staging position shown in FIGS. 4 and 5. The second staging position access direction 145 b has the advantage of introducing the overhead transfer flange 113 a to the overhead transfer conveyor 103 at a position along the length of moveable track 109 of the overhead transfer conveyor 103 that is very close to the position at which the overhead carrier support 111 a will support the overhead transfer flange 113 a, so that only a minimum of in-line, lateral motion between the overhead transfer flange 113 a and the overhead carrier support 111 a is required to enable the overhead transfer flange 113 a to lodge in the overhead carrier support 111 a. For example, during raising of the overhead transfer flange 113 a, a footprint of the overhead transfer flange 113 a may overlap a footprint of the overhead carrier support 111 a.

Referring to FIG. 6, the first blade receiver 121 a, the first blade surface 129 aa, and the rightmost extent 121 ae of the first blade receiver 121 a, all described above with reference to FIG. 5, are shown. The overhead transfer flange 113 a has begun to move in the in-line direction 107 (see FIG. 4) such that relative motion between the overhead transfer flange 113 a and the overhead carrier support 111 a is occurring. Specifically the overhead transfer flange 113 a has moved toward the overhead carrier support 111 a such that the first blade edge 129 ab is now directly above the first blade receiver lip 121 ad, and is aligned with the rightmost extent 121 ae of the first blade receiver 121 a.

A first clearance 147 a exists between the first blade edge 129 ab of the first blade 129 a and the lip 121 ad of the first blade receiver 121 a. In one embodiment of the invention, the first clearance 147 a is preferably about 3 mm or less, and more preferably about 1.5 mm or less. Other clearances may be employed in addition, a second clearance 147 b exists between the flange plate 125 (FIG. 2) of the overhead transfer flange 113 a and the support plate 115 of the overhead carrier support 111 a. In one embodiment of the invention, the second clearance 147 b is also preferably about 3 mm or less, and more preferably about 1.5 mm or less. Other clearances may be employed. It is preferable to keep clearances such as the first clearance 147 a and the second clearance 147 b at a minimum since space in the clean room of a typical semiconductor device manufacturing facility can be exceptionally expensive.

It should be noted that when the overhead transfer flange 113 a approaches the overhead carrier support 111 a along the in-line direction 107 (see FIG. 1) the first blade 129 a does not approach the first blade receiver 121 a directly (e.g., parallel to the cross sections of FIG. 5) such that a particular point along the first blade 129 a (e.g., point 129 aba along the first blade edge 129 ab of the first blade 129 a, as shown in FIG. 6) will pass in a normal direction to the first blade receiver 121 a and over a corresponding point (e.g., point 121 ada along the first blade receiver lip 121 ad, as shown in FIG. 6) on the first blade receiver lip 121 ad. Rather, a combination of normal convergence between the first blade 129 a and the first blade receiver 121 a (e.g., the “line” of the first blade edge 129 ab remains parallel with the “line” of the first blade receiver lip 121 ad while advancing toward the same) and lateral, relative motion between the first blade 129 a and the first blade receiver 121 a (e.g., the first blade edge point 129 aba moving laterally past the first blade receiver lip point 121 ada) will occur as the overhead transfer flange 113 a advances toward the overhead carrier support 111 a in the in-line direction 107 (see FIG. 1).

As such the respective points (not separately shown) along the overhead transfer flange 113 a and the overhead carrier support 111 a at which the cross-sections of FIGS. 5-8 and FIGS. 10-12 are taken are not all to be presumed to be those of cross-sections V-V of FIG. 4 but should instead be presumed to change from figure to figure according to the distance between the overhead transfer flange 113 a and the overhead carrier support 111 a, (e.g., cross sectional views taken at points on the overhead transfer flange 113 a and on the overhead carrier support 111 a close to that of section V-V of FIG. 4), without necessarily affecting the manner in which the overhead transfer flange 113 a and the overhead carrier support 111 a are depicted therein.

Referring to FIG. 7, the overhead transfer flange 113 a has moved further relative to the overhead carrier support 111 a such that the first blade edge 129 ab is directly above the first blade receiver's extended vertex 121 ac. With the overhead transfer flange 113 a in this position relative the overhead carrier support 111 a, the first blade 129 a can be allowed to drop relative to the first blade receiver 121 a along a vertical path 149 a such that the first blade edge 129 ab can achieve linear contact with the first blade receiver's extended vertex 121 ac.

Alternatively, the first blade 129 a can be urged further toward the first blade receiver 121 a along a horizontal path 149 b in the same horizontal plane, resulting in linear contact between the first blade edge 129 ab and the first blade receiver's second receiving surface 121 ab. As yet another alternative, the first blade 129 a can be moved through a sloping path 149 c having both horizontal and vertical components to achieve a similar result as that achieved via the sloping path 149 c. The sloping path 149 c in particular can be achieved by allowing the overhead transfer flange 113 a to lower or drop onto the overhead carrier support 111 a after the contribution of an initial horizontal velocity component.

As an example, the overhead transfer flange 113 a (e.g., the first carrier 105 a of which the overhead transfer flange 113 is a part) can be propelled horizontally at the same speed as the moveable track 109 of the overhead transfer conveyor 103 (e.g., by an arrangement of motorized rollers providing a horizontal conveying surface or by any other means). The horizontal speed of the first carrier 105 may be increased, causing the overhead transfer flange 113 a to “close” with the overhead carrier support 111 a and the first carrier 105 a (and the overhead transfer flange 113 a attached thereto) may be lowered or dropped relative to the overhead carrier support 111 a.

A curved path similar to the sloping path 149 c can begin when the lateral position of the overhead transfer flange 113 a relative to the overhead carrier support 111 a is as shown in FIG. 6, or even before the first blade edge 129 ab clears the first blade receiver lip 121 ad, as shown in FIG. 5, provided the overhead transfer flange 113 a passes over the first blade receiver lip 121 ad without striking the first blade receiver lip 121 ad, and contacts the first blade receiver's first receiving surface 121 aa, the first blade receiver's second receiving surface 121 ab, or the first blade receiver's extended vertex 121 ac.

Referring to FIG. 8, the overhead transfer flange 113 a is shown supported by the first blade receiver 121 a, with the first blade 129 a being lodged within the overhead carrier support 111 a. The first blade edge 129 ab is in linear contact with the first blade receiver's extended vertex 121 ac, and the first blade 129 a is in planar contact with the first blade receiver's first receiving surface 121 aa.

As an example, just prior to the first blade edge 129 ab achieving linear contact with the first blade receiver's extended vertex 121 ac, the first blade 129 a may have slid downward and rightward, with the first blade edge 129 ab sliding atop and in linear contact with the first blade receiver's second receiving surface 121 ab. In one embodiment of the invention, the first blade receiver's second receiving surface 121 ab is preferably oriented at about a 25-degree to a 30-degree angle to the vertical plane. Such an inclination ensures that the first blade 129 a will travel expeditiously downward from the point of contact of the first blade edge 129 ab with the first blade receiver's second receiving surface 121 ab. Other angles may be employed.

Alternatively, the first blade 129 a may have slid downward and leftward, with the first blade surface 129 aa sliding atop and in planar contact with the first blade receiver's first receiving surface 121 aa. In at least one embodiment of the invention, the first blade receiver's first receiving surface 121 aa is preferably oriented at about a 25-degree to a 30-degree angle to the vertical plane. Other angles may be employed.

While the first blade 129 a is seated within the first blade receiver 121 a (and the second blade 129 b is seated within the second blade receiver 121 b (see FIGS. 4-5)), the overhead transfer flange 113 a is advantageously restricted in both lateral directions and in the rearward direction (e.g., opposite the in-line direction 107 (see FIG. 1)) by the obstacle to the first blade surface 129 aa posed by the first blade receiver's first receiving surface 121 aa. In at least one embodiment of the invention, the blade and receiving surfaces are preferably flat and have complementary orientations with regard to the vertical to ensure close mating communication between the first blade surface 129 aa and the first blade receiver's first receiving surface 121 aa. As previously noted, the second blade receiver restricts lateral motion in the same manner. Non-flat surfaces also may be employed.

At the same time the overhead transfer flange 113 a is advantageously restricted in the forward direction (e.g., the in-line direction 107 (See FIG. 1)) by the obstacle to the first blade edge 129 ab posed by the first blade receiver's second receiving surface 121 ab. The first blade edge 129 ab may be somewhat rounded (e.g., a sharp corner that is broken, a radiused edge, a truncated cone, etc.) to ensure smooth sliding between the first blade edge 129 ab and the first blade receiver's second receiving surface 121 ab whenever the first blade edge 129 ab and the first blade receiver's second receiving surface 121 ab are caused to slidably communicate.

It should be noted, however, that communication between the first blade edge 129 ab and the first blade receiver's second receiving surface 121 ab is expected to occur almost exclusively during the process of depositing the overhead transfer flange 113 a upon the overhead carrier support 111 a. That is, once the first blade edge 129 ab is lodged within the first blade receiver's extended vertex 121 ac, and the first carrier 105 a (see FIG. 1) is being transported in the in-line direction 107 by the overhead transfer conveyor 103, there may be relatively little likelihood of the first carrier 105 a being subjected to a force tending to urge the overhead transfer flange 113 a forward relative the overhead carrier support 111 a. As will be explained further below, and with reference to FIGS. 9-12, it is more likely that the overhead transfer flange 113 a will be subjected to forces tending to urge it laterally, or forces tending to urge it rearwardly, or a combination of such forces.

FIG. 9 is a perspective cut-away view of a portion of the overhead transfer conveyor 103 utilizing the inventive coupling between the overhead carrier support 111 a and the overhead transfer flange 113 a to carry the first carrier 105 a in the in-line direction 107. An object 151, present in the path through which the overhead transfer conveyor 103 carries the first carrier 105 a, strikes a corner 105 aa of the first carrier 105 a. The object 151 may be a piece of machinery such as a robot that has moved away from its intended path due to a programming error, misplaced equipment or any other object. Many other objects or items may be placed, either intentionally or unintentionally, in positions near the overhead transfer conveyor 103 such that a collision with the first carrier 105 a may take place at the first carrier corner 105 aa.

Collisions with the first carrier 105 a may also be caused by objects (not separately shown) striking the bottom, side, top or rear of the first carrier 105 a. It would be unexpected for an object to strike the first carrier 105 a from behind, since the moveable track 109 of the overhead transfer conveyor 103 preferably carries substrate carriers at a high rate of speed in the in-line direction 107.

An advantage of the overhead carrier support 111 a and the overhead transfer flange 113 a of the present invention is that the first carrier 105 a can predictably and controllably dislodge from the overhead transfer conveyor 103 when subjected to a rearward or lateral force of a predetermined amount, such as, for example, 3 pounds or more, or preferably 5 pounds or more. That is, in one embodiment of the invention, if the first carrier 105 a is struck by a force of 1 or 2 pounds, directed toward the first carrier 105 a from the front or side, the overhead transfer flange 113 a preferably remains within the overhead carrier support 111 a so that the first carrier 105 a continues to be carried by the overhead transfer conveyor 103 in the in-line direction 107. However, if the first carrier 105 a is struck by a force of 7 or 8 pounds, directed toward the first carrier 105 a from the front or side, the overhead transfer flange 113 a preferably dislodges from the overhead carrier support 111 a and falls downward away from the overhead transfer conveyor 103 and away from the other substrate carriers being carried by the overhead transfer conveyor 103.

As described above and with respect to FIG. 1, when the first carrier 105 a is being carried by the overhead transfer conveyor 103 along the moveable track 109 in the in-line direction 107, lateral relative movement, front-to-rear relative movement, and rear-to-front relative movement on the part of the overhead transfer flange 113 a relative to the overhead carrier support 111 a is restricted, and in the normal operation of the overhead transfer conveyor 103, such movement is essentially prevented. Downward movement of the overhead transfer flange 113 a relative to the overhead carrier support 111 a is similarly restricted. Upward motion of the overhead transfer flange 113 a relative to the overhead carrier support 111 a however is generally unrestricted.

The object 151 depicted in FIG. 9 is likely to subject the first carrier 105 a to lateral and rearward forces which will vary depending on the speed of the overhead transfer conveyor 103 in the in-line direction 107, the angle at which the first carrier 105 a strikes the object 151, and the width of the first carrier 105 a (e.g., the distance from the moveable track 109 at which the collision between the object 151 and the first carrier 105 a takes place). The overhead carrier support 111 a, however, preferably restricts twisting and translating motion of the overhead transfer flange 113 a in the horizontal plane. As such, in order to prevent damage to the moveable track 109 of the overhead transfer conveyor 103, the horizontal forces resulting from the collision should be somehow redirected.

As viewed from the front of the overhead transfer flange 113 a in the in-line direction 107, the first blade receiver's first receiving surface 121 aa (FIG. 5) tilts backward, and the horizontally cropped chevron formed by the first blade receiver's first receiving surface 121 aa and its counterpart surface (not shown) on the second blade receiver 121 b (see FIG. 2) increases from a narrow aspect near the front of the overhead transfer flange 113 a to a wider aspect near the rear of the overhead transfer flange 113 a. This combination of two backward-tilting surfaces forming a rear-outward tapering chevron provides that the mating surface (e.g., the first blade surface 129 aa and its counterpart surfaces (not shown) on the second blade 129 b (see FIG. 2) may “ride” upward and rearward with regard to the overhead transfer flange 113 a, sliding along and in mating communication with their corresponding support surfaces as they ride.

In operation, the chevron-shaped arrangement of rearward and upward tilting surfaces just described, cooperates with rearward and lateral impact forces to which the first carrier 105 a may be subjected (e.g., during a collision) to cause the overhead transfer flange 113 a of the first carrier 105 a to move upward and rearward relative to the overhead carrier support 111 a of the overhead transfer conveyor 103. The overhead transfer flange 113 a may dislodge from the overhead carrier support 111 a, and thereby cause the first carrier 105 a to fall from the overhead transfer conveyor 103. This cooperation is explained below and with reference to FIGS. 10-12.

FIGS. 10-12 are cross-sectional views of respective portions of the first blade receiver 121 a of the overhead carrier support 111 a, and the first blade 129 a of the overhead transfer flange 113 a, which views depict the decoupling process that results in the first carrier 105 a dislodging from the overhead transfer conveyor 103. Referring to FIG. 10, the force F1 is applied to the overhead transfer flange 113 a normal to the direction in which the first blade 129 a extends as shown in FIGS. 5 and 6, and is a force derived from an impact between the first carrier 105 a and the object 151 as shown in FIG. 10.

If not for the obstacle posed by the first blade receiver's first receiving surface 121 aa to the lateral motion of the first blade 129 a of the overhead transfer flange 113 a, the force F1 would urge the first blade 129 a away from the first blade receiver 121 a in a lateral direction within the horizontal plane in which the overhead transfer flange 113 a is shown to reside in FIG. 8. However, because the first blade receiver's first receiving surface 121 aa blocks direct lateral movement of the overhead transfer flange 113 a due to the planar communication between the first blade receiver's first receiving surface 121 aa and the first blade surface 129 aa, the overhead transfer flange 113 a reacts to the force F1 by the first blade surface 129 aa sliding or “riding” upwards and rearward with respect to the overhead carrier support 111 a as a whole.

As described above, rearward motion of the overhead transfer flange 113 a relative to the overhead carrier support 111 a means that the point (not shown) on the overhead transfer flange 113 a at which the cross section of FIG. 10 is taken, moves into the page as the first blade surface 129 aa slides upward along the first blade receiver's first receiving surface 121 aa, and that cross-sections of the overhead transfer flange 113 a in FIGS. 10-12 are taken at different points of the overhead transfer flange 113 a.

Referring again to FIG. 10, in response to the force F1, the first blade surface 129 aa of the first blade 129 a rides up the first blade receiver's first receiving surface 121 aa of the overhead carrier support 111 a in direction 153, which is aligned with the slope 155 of the first blade receiver's first receiving surface 121 aa. Because the first blade surface 129 aa of the overhead transfer flange 113 a and the first blade receiver's first receiving surface 121 aa are in planar communication, and because complementary surfaces (not shown) on the other side of the overhead transfer flange 113 a operate at the same time, the overhead transfer flange 113 a can tend to retain, as it rises, the horizontal orientation it assumed while being carried by the overhead carrier support 111 a along the overhead transfer conveyor 103 (see FIG. 8) prior to the impact between the first carrier 105 a and the object 151 (see FIG. 9). In addition, the above-described arrangement of cooperating surfaces may cause the centerplane (not shown) of the overhead transfer flange 113 a to remain roughly aligned with the moveable track 109 of the overhead transfer conveyor 103 as the overhead transfer flange 113 a rises and moves rearward relative to the overhead carrier support 111 a.

Referring to FIG. 11, the overhead transfer flange 113 a has been fully dislodged from the overhead carrier support 111 a and is in upward projectile motion, as shown by projectile motion path 157, departing from the slope 155 of the first blade receiver's first receiving surface 121 aa. The overhead transfer flange 113 a is now no longer restricted in its vertical motion and may pass downward and away from the overhead carrier support 111 a.

The overhead transfer flange 113 a is shown in FIG. 11 to have risen such that the first blade edge 129 ab has at least achieved a clearance 147 c with respect to the first blade receiver's extended vertex 121 ac, which coincides with the height of the first blade receiver lip 121 ad above the first blade receiver extended vertex 121 ac. As such, the first blade edge 129 ab can pass above the first blade receiver lip 121 ad without risk of the first blade 129 a striking the first blade receiver 121 a. The clearance 147 c is preferably about 3 mm, it being noted that the extent of the clearance 147 c is to be selected based in part on the desired breakaway force, which in this embodiment is about 5 pounds, as described above. Should the desired breakaway force be less than 5 pounds, a lesser clearance 147 c may be selected, and vice-versa. For example, in another embodiment of the invention, a force of up to 20 pounds may be required to dislodge the first carrier 105 a from the overhead transfer conveyor 103. In such embodiments, a larger clearance 147 c may be desired (e.g., about 0.5 inches in one embodiment).

Referring to FIG. 12, the overhead transfer flange 113 a has passed rearward, downward and away from the overhead carrier support 111 a, with the progression of points on the first blade edge 129 ab describing the remainder of the projectile motion path 157. The first carrier 105 a (see FIG. 9) may now be caught in a net or other similar mechanism for gentle collection of the first carrier 105 a after the impact with the object 151 (see FIG. 9).

The foregoing description discloses only exemplary embodiments of the invention; modifications of the above disclosed apparatus and methods which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. For instance, the overhead carrier support lila and the overhead transfer flange 113 a may be formed from any suitable material (e.g., materials that slide freely and exhibit long term wear resistance). Exemplary materials for the overhead carrier support and/or the overhead transfer flange include metals (e.g., stainless steel, aluminum, etc.), plastics (e.g., polycarbonate, polyethelene, other ultra high molecular weight or high density plastics, nylon, PTFE, etc.), or other similar materials. Plastic components may be molded or otherwise fabricated.

FIG. 13 is a cross sectional view of a portion of the first blade receiver 121 a of the overhead carrier support 111 a and of the first blade 129 a of the overhead transfer flange 113 a illustrating an alternative embodiment of such components. With reference to FIG. 13, both the right most extent 121 ae of the first blade receiver 121 a and the first blade edge 129 ab of the first blade 129 a are angled at about 45 degrees from vertical (although other angles may be employed). Such a configuration provides a larger capture window for the overhead transfer flange 113 a than when the right most extent 121 ae and the first blade edge 129 ab are not angled. Also, when angled, these surfaces may slide relative to one another when misaligned and may assist in capture of the overhead transfer flange 113 a by the overhead carrier support 111 a.

While the overhead carrier support 111 a and the overhead transfer flange 113 a have been described herein primarily for use with overhead transport systems, it will be understood that the overhead carrier support 111 a (or portions thereof) may be employed to support and/or position a substrate carrier having the overhead transfer flange 113 a at any other location. For example, the overhead carrier support 111 a (or portions thereof) may be used for supporting and/or positioning substrate carriers within stockers, substrate carrier cleaners, local storage buffers that are part of a processing tool, batch process tools such as a furnace or a wet clean station, etc.

FIG. 14 is a perspective view of a plurality of shelves 175 a-b configured to support substrate carriers via an overhead transfer flange in accordance with the present invention. More or fewer than two shelves may be employed. Each shelf 175 a-b includes a support surface 177 a-b having blade receivers 121 a, 121 b coupled thereto (or formed therein). The shelves 177 a-b thus forms overhead carrier supports that may support substrate carriers having overhead transfer flanges such as the overhead transfer flange 113 a (FIGS. 1-12). The angles/dimensions of the blade receivers 121 a, 121 b may be, for example, similar to those described previously. The shelves 177 a-b may be mounted at any location at which a substrate carrier is to be supported (e.g., within stockers, substrate carrier cleaners, local storage buffers that are part of a processing tool, batch process tools, etc.). In one or more embodiments of the invention, the shelf 175 a and/or 175 b may be moveable. For example, the shelf 175 a and/or 175 b may be used to dock or undock a substrate carrier to/from a loadport of a processing tool.

FIG. 15 is a perspective view of the shelves 175 a-b of FIG. 14 wherein the top shelf 175 a supports a substrate carrier 179 via its overhead transfer flange 113 a. The substrate carrier 179 may be a single substrate carrier or adapted to house multiple substrate carriers. As will be apparent, use of the blade receivers 121 a, 121 b and the overhead transfer flange 113 a allows substrate carriers to be stacked with a high packing density and stored on and removed from storage shelves with relatively few movements.

The overhead transfer flange 113 a may be employed with open substrate containers or trays. The blade receivers of an overhead carrier support may be angled from front to back of the overhead carrier support (relative to horizontal); and/or the blade edges of an overhead transfer flange may be angled from front to back of the overhead transfer flange (relative to horizontal).

Accordingly, while the present invention has been disclosed in connection with exemplary embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims. 

1. An overhead carrier support adapted to support a substrate carrier having an overhead transfer flange, the overhead carrier support comprising: a support plate including a top and bottom surface; at least one coupling clamp fixed to the support plate and extending upwardly from the top surface, the at least one coupling clamp adapted to couple the overhead carrier support to a moveable track of an overhead transfer conveyor; a first side; a second side opposite the first side; a first blade receiver fixed below the support plate and including an upward facing groove, the first blade receiver and the upward facing groove further extending along the first side and adapted to receive a downwardly extending first blade of the overhead transfer flange of a substrate carrier; and a second blade receiver fixed below the support plate and including an upward facing groove, the second blade receiver and the upward facing groove further extending along the second side and adapted to receive a downwardly extending second blade of the overhead transfer flange of a substrate carrier; wherein the first blade receiver and the second blade receiver are angled at a third angle relative to each other such that the first blade receiver is oriented non-parallel to the second blade receiver and are adapted to allow a blade edge of the first blade and a blade edge of the second blade of the overhead transfer flange to settle into the first blade receiver and the second blade receiver, respectively, by a force of gravity.
 2. The overhead carrier support of claim 1 wherein the first blade receiver and the second blade receiver are oriented at substantially equivalent angles to a centerplane of the overhead carrier support.
 3. The overhead carrier support of claim 1 further comprising a flexible hanger fixed to the overhead carrier support, the flexible hanger extending from the upper surface of the support plate and adapted to provide further support for the overhead carrier support along the moveable track of the overhead transfer convey or.
 4. The overhead carrier support of claim 1 further comprising an angle of about 10 degrees to about 60 degrees formed inbetween the first blade receiver and the second blade receiver.
 5. The overhead carrier support of claim 1 wherein the first blade receiver and the second blade receiver are integrally formed with the support plate.
 6. The overhead carrier support of claim 1 wherein the overhead carrier support further comprises: a third side extending between the first side and second side; and a fourth side extending between the first side and second side, the fourth side further being opposite the third side and the fourth side wider than the third side.
 7. The overhead carrier support of claim 1 wherein the first blade receiver further includes a first receiving surface and a second receiving surface wherein at least one of the first receiving surface and second receiving surface is adapted to support the first blade.
 8. The overhead carrier support of claim 7 wherein the second blade receiver further has a first receiving surface and a second receiving surface wherein at least one of the first receiving surface and the second receiving surface is adapted to support the second blade.
 9. The overhead carrier support of claim 8 wherein the first surface and second surface of the first blade receiver form the upward facing groove, and the first surface and second surface of the second blade receiver form the upward facing groove.
 10. A system adapted to support a substrate carrier on an overhead transfer conveyor comprising: an overhead carrier support adapted to couple to an overhead transfer flange of the substrate carrier and to the overhead transfer conveyor, the overhead carrier support further comprising: a support plate including a top and bottom surface; a first side; a second side opposite the first side; a first blade receiver fixed below the support plate and including an upward facing groove, the first blade receiver and the upward facing groove further extending along the first side, the first blade receiver adapted to receive a first blade of the overhead transfer flange; and a second blade receiver fixed below the support plate and including an upward facing groove, the second blade receiver and the upward facing groove further extending along the second side and adapted to receive a second blade of the overhead transfer flange; wherein the first blade receiver and second blade receiver are angled at a third angle relative to each other such that the first blade receiver is oriented nonparallel to the second blade receiver; and wherein the first blade receiver and second blade receiver are adapted to allow a blade edge of the first blade and second blade of the overhead transfer flange to settle into the first blade receiver and the second blade receiver, respectively, by a force of gravity.
 11. The system of claim 10 wherein the first blade receiver further comprises a first receiving surface and a second receiving surface.
 12. The system of claim 11 wherein the first receiving surface of the first blade receiver is inclined at an angle of between about 25 degrees and about 30 degrees to a vertical plane that coincides with a centerplane of the overhead carrier support.
 13. The system of claim 11 wherein the second receiving surface of the first blade receiver is inclined at an angle of between about 25 degrees and about 30 degrees to a vertical plane that coincides with a centerplane of the overhead carrier support.
 14. The system of claim 10 wherein the second blade receiver further comprises a first receiving surface and a second receiving surface.
 15. The system of claim 14 wherein the first receiving surface of the second blade receiver is inclined at an angle of between about 25 degrees and about 30 degrees to a vertical plane that coincides with a centerplane of the overhead carrier support.
 16. The system of claim 14 wherein the second receiving surface of the second blade receiver is inclined at an angle of between about 25 degrees and about 30 degrees to a vertical plane that coincides with a centerplane of the overhead carrier support.
 17. The system of claim 10 wherein the overhead transfer flange further comprises a first blade and second blade adapted to mate with the first blade receiver and the second blade receiver of the overhead carrier support such that lateral motion of the overhead transfer flange relative to the overhead carrier support is restricted.
 18. A system adapted to support a substrate carrier on an overhead transfer conveyor comprising: an overhead carrier support adapted to couple to an overhead transfer flange of the substrate carrier and to the overhead transfer conveyor, the overhead carrier support further comprising: a support plate including a top and bottom surface; a coupling clamp fixed to the support plate and extending upwardly from the top surface, the at least one coupling clamp adapted to couple the overhead carrier support to a moveable track of an overhead transfer conveyor; a first side; a second side opposite the first side; a first blade receiver fixed below the support plate and extending along the first side, the first blade receiver adapted to receive a first blade of the overhead transfer flange, the first blade receiver including a first receiving surface and a second receiving surface forming an upward facing groove, wherein at least one of the first receiving surface and the second receiving surface is adapted to support the first blade and further wherein at least one of the first receiving surface and the second receiving surface is adapted to slidably communicate with a blade edge of the first blade of the overhead transfer flange; and a second blade receiver fixed below the support plate and extending along the second side and adapted to receive a second blade of the overhead transfer flange the second blade receiver further including a first receiving surface and second receiving surface forming an upward facing groove wherein at least one of the first receiving surface and the second receiving surface is adapted to support the second blade and further wherein at least one of the first receiving surface and the second receiving surface is adapted to slidably communicate with a blade edge of the second blade of the overhead transfer flange; wherein the first blade receiver and the second blade receiver are angled at a third angle relative to each other such that the first blade receiver is oriented nonparallel to the second blade receiver; and wherein the first blade receiver and the second blade receiver are adapted to allow the blade edge of the first blade and a blade edge of the second blade of the overhead transfer flange to settle into the first blade receiver and the second blade receiver, respectively, by a force of gravity.
 19. A system adapted to support a substrate carrier on an overhead transfer conveyor comprising: an overhead carrier support adapted to couple to an overhead transfer flange of the substrate carrier and to the overhead transfer conveyor, the overhead carrier support further comprising: a support plate including a top and bottom surface; a coupling clamp fixed to the support plate and extending upwardly from the top surface of the support plate, the coupling clamp adapted to couple the overhead carrier support to a moveable track of the overhead transfer conveyor; a flexible hanger fixed to the support plate and extending upwardly from the top surface of the support plate, the flexible hanger adapted to provide further support for the overhead carrier support along the moveable track of the overhead transfer conveyor; a first side; a second side opposite the first side; a first blade receiver fixed below the support plate and including an upward facing groove, the first blade receiver and the upward facing groove further extending along the first side, the first blade receiver adapted to receive a first blade of the overhead transfer flange, the first blade receiver further including a first receiving surface and second receiving surface wherein at least one of the first receiving surface and the second receiving surface is adapted to support the first blade, and further wherein at least one of the first receiving surface and the second receiving surface is adapted to slidably communicate with a blade edge of the first blade, the first and second receiving surfaces forming a first vertex at an intersection between the first receiving surface and second receiving surface; and a second blade receiver fixed below the support plate and including an upward facing groove, the second blade receiver and the upward facing groove further extending along the second side and adapted to receive a second blade of the overhead transfer flange the second blade receiver further including a first receiving surface and a second receiving surface wherein at least one of the first receiving surface and the second receiving surface is adapted to support the second blade, and further wherein at least one of the first receiving surface and the second receiving surface is adapted to slidably communicate with a blade edge of the second blade, the first receiving surface and the second receiving surface forming a second vertex at an intersection between the first receiving surface and second receiving surface; wherein the first blade receiver and the second blade receiver are angled at a third angle relative to each other such that the first blade receiver is oriented non-parallel to the second blade receiver; and wherein the first blade receiver and the second blade receiver are adapted to allow the blade edge of the first blade and a blade edge of the second blade of the overhead transfer flange to settle into the first blade receiver and the second blade receiver, respectively, by a force of the gravity. 